Gantt remains blank when more than the limit should be loaded.

Any error in projeqtor log file or in browser console.

There is somme issue for sure.
We must find the loggued error.

First, search in Apache or PHP error log for errors (just produce the anomaly to be sure to gt the correct timeframe in the log)

If you don't find errors in logs, try this workaround :
Open the browser console.
Go to tab "network"
Play the case that generate the issue
On the network log, serach for call to jsonQuery.php : select it
Int the right part, select tab response : you should bet a json text
At the end of the json text, you should get an error message : post it here.